Your tractor was built in 1972, note the Product Identification plate is after the second merger of Oliver and MM when headquarters was relocated to Butterfield, Il.
Top row of numbers: 515 is the model number, a late 550, last model built. Following the dash after 515 the 7 means it was built as a 2 wheel drive Industrial. 1 means it was built with a gas engine. Last three is how the tractor was assembled.